How can I use Mesh as a Tile on Geometry?
See Duplication and Particles/Hair.  I am trying to give a quick answer to get you started on research.  

Some of these have scale to face area features.

See this 
Tapering a tentacle mesh with uniformly scaled suction discs

Particles can have texture in (Strand/Particles) coordinates. The texture can control size of particles.  The texture may be a superior and more forthwith solution rather than size of tiles.

This proposed answer is not a tutorial. Seeing duplication and particles may be fun. Please search at BSE and the famous video site that rhymes with noonoob.   Keywords Blender Particles Duplication Dupliverts Duplifaces.

These concepts can involve some hours of work as you become more skilled with them.